1. Field of the Invention
The present invention relates to a connection structure of a lateral insert type yoke and a shaft, used for a steering device etc of an automobile, for connecting the shaft to the lateral insert type yoke with its one side end to which a universal joint is connected.
2. Related Background Art
A steering device for giving a steering angle to a front wheel of the automobile is generally constructed to transfer a motion of a steering shaft rotating with an operation of a steering wheel to an input shaft of a steering gear via a spider type universal joint.
This universal joint is constructed such that a couple of U-shaped yokes are axially supported each other via a spider or cross shaft. In the case of assembling the steering device by use of this type of universal joint, for example, one yoke is previously joined and fixed by welding or fastening with a screw to a side end of one shaft such as the steering shaft etc, and the other yoke is joined to a side end of the other shaft. Normally, for executing this assembling operation, after one shaft has been supported on a vehicle body, this shaft and the other shaft are joined through the universal joint. Accordingly, what is preferable is a so-called lateral insert type yoke in which at least one yoke of those two yokes of the universal joint can perform the fixing operation without moving the shaft in an axial direction.
This lateral insert type yoke is constructed of a member constituting one part of the universal joint, and a joint member provided integrally with this member and taking a U-shape in section within a plane orthogonal to the axial direction. A side end of the shaft taking a sectional configuration suited to the concave of the U-shape, is inserted sideways from an opening into the concave area of the U-shaped joint member then, two pieces of side end portions extending in parallel of the U-shape are penetrated, screwed and fastened with a bolt, thereby joining the shaft to the lateral insert type yoke. On this occasion, it is a general practice that a cam (cam member) provided integrally with the bolt or given a predetermined frictional resisting force performs positioning (centering) within the joint member of the shaft.
Thus, an assembling method in the conventional connection structure of the lateral insert type yoke and the shaft, in which the cam provided at the bolt performs centering of the shaft, is roughly classified into two types. One type is, as disclosed in, e.g., Japanese Patent Application Laid-Open Publication No. 10-318272, that the nut is fastened by use of a cam bolt. The other type is, as disclosed in Japanese Patent Application Laid-Open Publication Nos. 10-169664 and 10-148215, that the bolt is fastened.
In the former assembling method in the conventional connection structure of the lateral insert type yoke and the shaft, for convenience of fastening the nut, the assembling operation is required to be carried out in the following way. After the bolt has been inserted from backward, and a front side end of the bolt is protruded on the near side, or after the bolt has been inserted from the near side, the universal joint is rotated through 180 degree, and the nut is set on the near side. However, the intrusion of the bolt from the backward may be done by groping invisible to eyes, which might not be easy. Further, a labor is needed for rotating the universal joint through 180 degrees, resulting in an increase in the number of steps of the operation.
Moreover, there is needed a bolt temporary holding mechanism for supporting the bolt so as not to be pushed backward till the nut is screwed once or twice along the front side end of the bolt. The head of the bolt must be held by turning the hands backwards if this mechanism is not used. This operation is laborious enough to use both of the hands. Thus, some problems have existed in the former method.
Further, in the latter assembling method, the bolt is inserted from the near side and fastened as it is. Therefore, unlike the former method, there is no necessity of inserting the bolt from backward and rotating the universal joint through 180 degree. When in the assembly, it is required for ensuring the fastening by a tool that after the bolt has been inserted by the hand, the front side end of the screw portion of the bolt is lightly screwed once or twice into the nut fixed to the yoke or into a thread portion (thread forming portion) of the yoke, and final fastening is effected. As described above, however, the cam member of the bolt is fitted to the screw portion with a predetermined frictional resisting force, and a load resistance for rotating the bolt is large. Hence, there arises a problem, wherein the front side end of the screw portion can not be lightly screwed into the nut or the thread portion of the yoke by pinching the head of the bolt.
According to the former method of those assembling methods, for the convenience of fastening the nut, after the bolt has been inserted from backward, the front side end of the bolt is protruded on the near side, or after the bolt has been inserted from the near side, the universal joint is rotated through 180 degrees, and it is required that the nut be set on the near side. According to the latter method of fastening the bolt, however, the bolt is inserted from the near side and fastened as it is. Therefore the latter method has more of operability than the former method.
According to the assembling method of fastening the bolt on the near side, however, the nut is required to be fitted to the yoke so as not to come off or rotate. Further, there is a drawback in which a shaft 203 inserted into a yoke 201 is, as shown in FIG. 23, easy to come off till the bolt is inserted and at first screwed into the nut, and hence the assembly needs an operation while supporting the shaft 203 with the hands.
Such being the case, there have been proposed several assembling methods capable of fastening the bolt without supporting the shaft with the hands. Patent Publication No. 2735260 discloses that a special nut including a rotation stopper and a bolt-insert-sided portion formed comparatively long, is slidably held in a nut hole of the yoke by use of a leaf spring member, and, after inserting the shaft into the yoke, the shaft is held by the bolt-insert-sided portion of the nut.
Further,. U.S. Pat. No. 5,358,350 discloses that a temporary holding clip taking substantially a C-shape and including an engagement portion defined as a protruded member with its one side end warped outwards, is fitted into one side end of the yoke with this engagement portion being set inwards, when the shaft is inserted, the engagement portion is pushed to permit the shaft to pass through, the warp of the engagement portion elastically reverts after the shaft has passed through, and this engagement portion engages with the shaft, thus temporarily holding the shaft.
Japanese Patent Application Laid-Open Publication No. 11-280777 discloses that a shaft 203 is, as shown in FIG. 24, let through a hole 214 of a temporary stopper 208 for joint, when set in a concave portion of a yoke 201, a pawl 215 of the joint temporary stopper 208 is caught by a rear surface side of the yoke 201, and the shaft 203 is thereby temporarily held.
Japanese Patent Application Laid-Open Publication No. 1130241 discloses that a clip 220 having, as shown in FIG. 26, a protruded portion 220a elastically shiftable in an arrow direction, is internally fixedly fitted into a bolt hole 211e of a yoke 201 as shown in FIG. 25, when the shaft 203 is inserted from an arrow direction, the protruded portion 220a is intruded into the bolt hole 211e to permit the shaft 203 to pass through, when the shaft 203 is fitted into the concave portion of the yoke 201, the protruded portion 220a elastically reverts to its original shape, and the front side end of the protruded portion engages with the shaft 203.
The Japanese Patent Application Laid-Open No. 11-280781 discloses that, when inserting the shaft protruded portions 330a provided in a bolt through-hole 330b of a clip 330 are intruded into the bolt hole of the yoke, as shown in FIG. 27, to permit the shaft to passthrough, however, when the shaft is fitted into the concave portion of the yoke, the protruded portions 330a elastically return to prevent the shaft from separating from the yoke.
Further, Japanese Utility Model Laid-Open Publication No. 6-78630 discloses that engagement holes are formed two internal side surfaces facing to each other within the yoke, engagement protrusions each having a size suited to fitting into each of the engagement holes are provided on an engagement cylinder externally fitted to the front side end of the shaft, when the shaft externally fitted with the engagement cylinder is inserted into the yoke, the engagement protrusions are fitted into the engagement hole, and the shaft is thus temporarily held by the yoke.
Among the conventional shaft temporary holding structures of the lateral inset type yokes, however, the structure disclosed in Patent Publication No. 2735260 has such a problem that the special nut formed with the rotation stopper involves a high cost, and besides the nut might come off when screwed by applying the bolt.
Further, the following is a problem inherent in the structure disclosed in U.S. Pat. No. 5,358,350. A temporary holding clip 421 is, as shown in FIG. 28, attached to one side end of a yoke 401, and a spacing d from the clip 421 needs to be provided for permitting the shaft 403 to pass through. This spacing d, however, becomes large when considered in terms of a size of the clip 421, and the two side ends of the yoke 401 diverge if the shaft 403 is set in this position. Therefore, it takes an extra time corresponding to the operation of fastening these two side ends by the bolt.
Moreover, according to Japanese Patent Application Laid-Open Publication No. 11-280777 illustrated in FIG. 24, a drawback is caused, wherein it is necessary that the assembly be done after letting the shaft 203 through the hole 214 of the joint temporary stopper 208, and the shaft 203 can not be inserted while the joint temporary stopper 208 is kept fitted to the yoke 201.
Further, according to Japanese Patent Application Laid-Open Publication No. 11-030241 illustrated in FIGS. 25 and 26, there is caused the following drawback. The front side end of the bolt catches the protruded portion 220a of the clip 220 when inserting the bolt, and hence the clip 220 might come off inwardly of the yoke 201. Further, when the clip 220 is attached to the yoke 201, there is no process of positioning the clip 20 in a rotational direction of the bolt in order to determine a direction of the protruded portion 220a, and hence an arbitrary positioning process must be executed.
In addition, according to Japanese Patent Application Laid-Open No. 11-280781, as shown in FIG. 29, a fitting portion 530c of the clip is inserted and fitted into a nut hole 511d of the yoke. Therefore, the nut hole 511d is required to be formed larger than a diameter of a bolt 506. For this reason, a backlash of the bolt 506 is large, with the result that a deviation easily occurs in centering of the shaft when assembled. Moreover, when fastening the bolt 506, the fitting portion 530c is interposed between the bolt 506 and the yoke, and this therefore causes a slack of the bolt.
Further, a problem inherent in Japanese Utility Model Laid-Open Publication No. 06-78630 is that the engagement hole needs to be formed in the internal side surface of the yoke, and working for this formation is not easy and leads to an increase in cost.
It is a first object of the present invention to provide a connection structure of a yoke and a shaft, which is capable of screwing a bolt into a yoke by a simple operation and of performing centering of the shaft in a construction where the bolt is inserted from a near side and fastened as it is.
To accomplish this object, according to one aspect of the present invention, a connection structure of a yoke and a shaft comprises a shaft including a pair of flat surfaces formed in parallel to each other on an outer peripheral surface of a front side end thereof, a yoke having a connection portion, formed at one side end thereof, for connecting the shaft, and having the other side end connected to a universal joint. The connection portion includes holding members, for holding the flat surfaces of the shaft, taking substantially a U-shape in section within a plane orthogonal to an axial direction thereof, a screw hole formed in the vicinity of one side end of the U-shape, and a bolt hole formed in the vicinity of the other side end thereof, concentric with the screw hole and having a diameter larger than the screw hole. This connection structure functions to insert from the bolt hole a bolt externally fitted with a cam member having a fitting hole by inserting the shaft in between the holding members, then screw the bolt into the screw hole, thus join the shaft to the joint portion, and perform centering of the shaft with the rotations of the cam member. The cam member is movable on the bolt facing at least a part of the shaft in the axial direction of the bolt, and the bolt is provided with a frictional engagement portion frictionally engaging with the cam member and rotating the cam member when the bolt is screwed into the screw hole and fastened thereto.
Further, according to the present invention, the part of the shaft may include a screw portion of the bolt, the frictional engagement portion of the bolt may include a large-diameter portion having a diameter larger than a diameter of the fitting hole of the cam member that is formed between the screw portion and a head of the bolt, and the large-diameter portion may be press-fitted into the fitting hole when the bolt is screwed into the screw hole and fastened thereto.
According another aspect of the present invention, a connection structure of a yoke and a shaft comprises a shaft including a pair of flat surfaces formed in parallel to each other on an outer peripheral surface of a front side end thereof, a yoke having a connection portion, formed at one side end thereof, for connecting the shaft, and having the other side end connected to a universal joint. The connection portion includes holding members, for holding the flat surfaces of the shaft, taking substantially a U-shape in section within a plane orthogonal to an axial direction thereof, a screw hole formed in the vicinity of one side end of the U-shape, and a bolt hole formed in the vicinity of the other side end thereof, concentric with the screw hole and having a diameter larger than the screw hole. This connection structure functions to insert from the bolt hole a bolt externally fitted with a cam member having a fitting hole by inserting the shaft in between the holding members, then screw the bolt into the screw hole, thus connect the shaft to the joint portion, and perform centering of the shaft with the rotations of the cam member. An inside diameter of the fitting hole of the cam member has a dimension enough to be movable with respect to a screw portion of the bolt. The bolt is provided with a large-diameter portion between the screw portion and the head, having such an outside diameter larger than an inside diameter of the fitting hole and a length as to be press-fittable into the fitting hole and to generate a frictional resisting force capable of centering after being press-fitted, and the screw portion is set to such a length that at least the large-diameter portion is not press-fitted into the fitting hole till a front side end of the screw portion is at first screwed into the screw hole.
With the construction described above, when the front side end of the screw portion of the bolt is at first screwed into the screw hole, the cam member is still movable on the bolt in the axial direction of the bolt, so that the bolt can be lightly screwed in twice or three times by pinching the head with the fingers. Thereafter, when the bolt is further screwed and thus fastened, the frictional engagement portion of the bolt frictionally engages with the cam member, thereby generating a frictional resisting force. Therefore, the bolt can not be screwed by fingers but can be screwed by a tool. The cam member thereby rotates with the rotations of the bolt, and the cam member intrudes the shaft into the concave portion of the U-shaped holding members, thus performing the centering.
It is a second object of the present invention to provide a shaft temporary holding clip of a lateral insert type yoke that is capable of temporarily holding the shaft so as not to come off till a bolt is screwed into a nut after the shaft has been inserted into the yoke, and preventing an interference with a fastening operation of the bolt with a simple construction.
To accomplish the second object, according to a further aspect of the present invention, there is provided a shaft temporary holding clip of a lateral insert type yoke, for connecting a shaft including a pair of flat surfaces formed in parallel to each other on an outer peripheral surface of a front side end thereof to its one side end, and connecting the other side end thereof to a universal joint. The clip comprises holding members, of which a portion for joining the shaft is formed in a U-shape in section within a plane orthogonal to an axial direction thereof, for holding the flat surfaces of the shaft, a nut hole, formed in the vicinity of a side end of one of the holding members, into which a nut is internally fixedly fitted, a bolt hole, formed in the vicinity of a side end of the other of the holding members, concentric with the nut hole and having a diameter larger than the nut hole, the clip working to temporarily hold the shaft till the bolt is inserted from the bolt hole and screwed into the nut after the shaft has been inserted in between the holding members, and being attached to a predetermined position of the holding members, a fitting portion externally fitted to a side end of one of the holding members inwards from outside along its configuration, a support portion formed so as to protrude from an internal side end portion of the fitting portion in a direction more inclined inwards by a predetermined angle than in a direction orthogonal to the axial direction of the bolt, of which a flexure acting in an outer direction with the internal side end serving as a fulcrum falls within a limit of elasticity, and an engagement portion integrally formed at a front side end of the support portion, and internally fitted into the nut hole or the bolt hole so as to be movable in the axial direction of the bolt. A part of the shaft slides while pushing the support portion when inserting the shaft in between the holding members. The engagement portion thereby moves back into the nut hole or the bolt hole to permit the shaft to pass through, and when the shaft is intruded into a concave area between the holding members, the engagement portion elastically returns to an original position and engages with the shaft.
With this construction, the shaft is inserted in between the holding members intruded into the concave portion of the holding members, at which stage the pressing of the shaft upon the support portion is canceled. The engagement portion thereby elastically returns to its previous position and engages with (temporary holds) the shaft. Accordingly, the bolt is screwed into the nut with a single hand without supporting the shaft with the hands, and can be fastened as it is.